1. Field of the Invention
The invention relates to improved field incubators for solitary-nesting pollinating bees and methods for rearing and managing such bees.
2. Description of the Prior Art
In the United States, honey bees have been typically looked upon as the only pollinator of our farm crops. Domestic hives of bees are rented and placed as needed to facilitate pollination. More than 2 million honey bee colonies are rented each year in the United States. Over $14 billion worth of crops nationwide rely upon pollination by insects, and of these, honey bees have carried the largest portion of the pollination work load. Most fresh fruit and vegetable, nut and seed crops rely upon insect pollination, including almonds, apples, blueberries, peaches, strawberries, cherries, melons, pears, plums, pumpkins and squash. Many seed crops also rely on insect pollination, including alfalfa, canola, sunflowers, carrots, and onions.
On most crops, honey bees can and do in fact provide an adequate job of pollinating. However, for some crops the honey bee provides only marginal pollination. This may be due to any of a variety of reasons including blooming patterns and blossom/flower anatomy. For instance, some crops bloom at lower temperatures and hence prior to the activity temperature of the honey bee. The blossoms and flowers of other plants may also have petal patterns which make it difficult for the honey bee to successfully pollinate that flower. In other situations, honey bees prefer to forage on other plants providing more abundant pollen or nectar than the target crop.
Of far greater concern however, has been the precipitous decline in the number of honey bees available for pollination. In the last 10 plus years, North American honey bees have come under unprecedented attack from 3 different sources. As a consequence, many beekeeping operations have been forced out of business, creating a critical shortage of honey bees for pollination in some areas. For example, in 1981 Pennsylvania had 85,000 commercial bee hives. By 1995, that number was reduced to 27,000 hives (Penn State Agriculture, Winter/Spring 1998). Other states have suffered similar losses, including Maine—80%, New Jersey—60%, New York—60-70%, Delaware—25-40%, Michigan—60%, and Wisconsin—67%. Wild honey bee populations have suffered as well. It has been estimated that the Northeast may have lost as many as 80% of its wild honey bees.
The causes for the bee colony losses have primarily been attributed to two parasites, tracheal mites and Varroa mites. Various treatments have been tried, and experiments with other methods and treatments are continuing in an effort to control these parasites. The results have been mixed and none are completely satisfactory. These parasites, compounded with poor weather and other mitigating factors, have left farmers and orchardists scrambling to find adequate pollinators for their crops.
To compound the problem with these mites, the Africanized honey bee (a cross between the European honey bee and African bees) has infiltrated Texas, New Mexico, Arizona, and California, and populations of these bees are steadily progressing Northward, bringing with them their hostile behavior and propensity for multiple stings. This has made it ever increasingly difficult to locate bee colonies for crop pollination in close proximity to populated areas.
Unfortunately, it has been the small to medium sized farm and farmers that have felt the pinch most severely. In this period of shortage, the suppliers of rented honey bee colonies have naturally catered to their larger accounts, and the smaller farms have been seriously in need of a pollinator for their crops. Moreover, it is often the small farmer who is found working the smaller pieces of ground located close to or amongst homes and commercial areas, where complaints from residents over permanent or rented honey bee colonies have prompted concerns and conflicts.
In view of these mounting problems, investigators and users have attempted to develop alternatives to the honey bee for pollinating crops. For instance, in recent years bumble bees have been increasingly used in the pollination of greenhouse tomatoes and other greenhouse crops. Solitary bees have also shown promise as alternative pollinators. One of these, the alfalfa leafcutting bee, Megachile rotundata, has been used for years in the production and growing of alfalfa seed. In 1990, 2.2 billion alfalfa leaf cutting bees, worth nearly $11 million, were used in the U.S. to pollinate alfalfa seed production acreage. In 1976, Phil Torchio at the USDA Agricultural Research Service, Bee Biology Systematics Laboratory in Logan, Utah, initiated investigations into the use of the blue orchard bee, Osmia lignaria Say (Hymenoptera: Megachilidae) (also known as the orchard mason bee). The use of these and other solitary bees as pollinators have been reviewed by Jesiolowski (1996, Organic Gardening, May/June, pp. 28-35) and Schuessler (1998, Frontier Magazine, September/October, pp. 20-23).
Solitary bees have demonstrated several highly desirable characteristics and advantages over honey bees which make them advantageous for use as pollinators on several crops. Most notably, the solitary bees are more efficient pollinators of many crops than honey bees, requiring far fewer bees to pollinate a field or orchard than honey bees. Moreover, some solitary bees are typically active in early spring, often before honey bees reach their optimum activity. For instance, the blue orchard bee will fly at temperatures about 5° C. lower than honey bees, and will fly more on overcast days and in higher humidity. As such, they are ideal for early spring crops and blossoms which need pollination during the typically poorer weather of this period. Other advantages of note include their gentle nature, and their insusceptibility to the parasites that have recently decimated honey bee populations. Moreover, solitary bees cannot hybridize with African or Africanized honey bees.
The blue orchard bee is a particularly efficient pollinator of orchard flowers. Orchard pollination proficiency is due to the bee's natural emergence in the spring, preference for the nectar and pollen of fruit tree flowers, and promiscuous foraging behavior (Torchio, 1976, J. Kansas Entomol. Soc. 49: 475-482; Torchio, 1985, J. Kansas Entomol. Soc. 58: 448-464; Torchio, 1987, Proc. Entomol. Soc. Ontario 118: 111-124; Bosch et al., 2006, J. Econ. Entomol. 99: 408-413; Bosch and Kemp, 2001, How to manage the blue orchard bee as an orchard pollinator. Sustainable Agricultural Network, Handbook No. 5, Beltsville, Md.; Bosch and Kemp, 2002, Bull. Entomol. Res. 92: 3-16, 2002). This univoltine species is a cavity-nesting bee that naturally occurs throughout most of the United States and into southern Canada (Rau, 1937, Ann. Entomol. Soc. Am. 30: 324-343; Mitchell, 1962, Bees of the eastern United States, Vol. II. Tech. Bull. No. 152, North Carolina Exp. Sta., 557 pp). The adult bees overwinter in their cocoons and in the spring readily will emerge within a few days when exposed to warm temperatures (Bosch and Kemp, 2001, ibid). Commercial management of blue orchard bees includes maintaining them in artificial nesting cavities and subjecting them to defined temperature regimes during winter and spring to facilitate emergence of adults in synchrony with orchard bloom. With care and proper management, a blue orchard bee population can be sustained and increased, thus allowing an orchardist to maintain a supply or surplus of pollinators (Torchio 1976, 1985, 1987; Bosch et al. 2006; Bosch and Kemp 2001, 2002, all ibid).
Blue orchard bees can be used alone, or in addition to honey bees, for fruit tree pollination. One problem that has hindered the use of any bees for pollinating almonds is that almond trees bloom early in the spring when temperatures can still be cool enough to inhibit bee emergence and foraging activity (Torchio, 1976, ibid). The blue orchard bees will fly under overcast skies and at lower temperatures (12° C.) than honey bees (Bosch and Kemp 2001, ibid), yet may be slow to emerge from their cocoons under field conditions. Especially for female bees, cool field temperatures can inhibit the bees' quick and synchronous emergence. A consequence of slow, asynchronous emergence is that many bees may still be in their cocoons when the earliest, most productive almond bloom occurs (Delaplane and Mayer, 2000, Crop pollination by bees. CABI, New York, USA, 344 pp.). Because the cross-pollination of nearly 100% of almond flowers is required for adequate crop production (Delaplane and Mayer, 2000, ibid), overall fruit yield may be suboptimal if some flowers demise before pollinator foraging ensues.
If the blue orchard bees are wintered for sufficiently long periods, and if the maximum daily temperatures are above 20° C., then incubating bees after their wintering period is not necessary. However, only sometimes will the unpredictable spring weather provide conditions that allow for synchronous emergence of bees and bloom. Sometimes conditions can be such that bee emergence is arrested while bloom continues to progress. For example, various cultivars of almonds will progress towards bloom by accumulating heat units at base temperatures ranging from 1.1-8.9° C. (DeGrande-Hoffman et al., 1996, J. Appl. Ecol. 33: 812-818), while blue orchard bees seem to progress towards emergence at temperatures above 5° C. (Bosch and Kemp, 2001, ibid). Considering various factors related to successful fruit set in almonds, the optimum temperatures influencing flight of pollinators, germination of pollen, pollen tube growth, and maintenance of ovule viability are considered to be 15-25° C., and temperatures outside of this range can be inhibiting [Kester and Gradziel, 1996, Almonds, in: Janick J., Moore J. N. (Eds.), Fruit Breeding, Vol. III. Nuts, John Wiley & Sins, Inc., New York, N.Y., pp. 1-97].
If the timing of fruit tree blossom is ahead of that of bee emergence, blue orchard bee nests containing wintered adults can be incubated under artificial conditions away from the orchard, and the adults can be collected in containers and released into the field (Torchio 1981, J. Kansas Entomol. Soc. 54: 824-836; Torchio, 1982, J. Kansas Entomol. Soc. 55: 759-778; Bosch and Kemp, 2001, ibid). However, females released as emerged adults express higher pre-nesting dispersal rates (Torchio, 1984, J. Kansas Entomol. Soc. 57: 517-521; Torchio, 1985, ibid), thus diminishing female establishment and reproduction in the orchard.
Efforts to introduce and rear these and other solitary bees in orchards and fields have typically involved the provision of nesting blocks in which the bees will nest and lay eggs. Most common nesting blocks are simply formed from blocks of wood into which small holes have been drilled into one face thereof, and into which paper straws may be optionally inserted. Alternatively, nesting blocks are formed from clusters of conventional drinking straws packed into a container with one end left exposed (see Jesiolowski, ibid). However, wooden nesting blocks tend to be difficult to disinfect and are heavy and difficult to drill and handle. If these blocks are not properly disinfected, any eggs laid therein will be susceptible to disease.
McCarthy (U.S. Pat. No. 4,765,007) has disclosed a nesting block for the alfalfa leaf cutter bee which is formed from a block of molded polystyrene having a plurality of holes extending therethrough. These holes are closed on one end by application of a backing sheet onto one face of the block. In all of these designs, a single adult female bee will form cells within the holes or straws, with each cell having a ball of pollen or nectar upon which a single egg is deposited. Adjacent cells within any one hole or straw are separated from one another by partitions formed from mud or plant parts which differ with each species of cavity nesting solitary bee. After nests have been laid and the adult bees have pollinated the area in the vicinity of the block, the blocks may be collected and stored for use in the next year. When placed in the field the following season, adult bees will emerge from the nests and repeat the cycle.
More recently, Kendell et al. developed an improved nesting block for the rearing and management of cavity nesting solitary bees used for pollinating crops. This nesting block included a chamber having at least one substantially flat face and a plurality of tubes which extended from the face into the chamber from the face. The chamber was formed from an organic polymeric material, a major portion of which was polycarbonate.
However, despite these advances, the need persists for improved material and techniques for rearing and managing solitary bees before they can be used on an increasing scale as crop pollinators.